Sealing strip

ABSTRACT

A ROTARY PISTON MACHINE IN WHICH ONE OF TWO MEMBERS ROTATABLE RELATIVE TO EACH OTHER HAS GUIDED IN POCKETS THEREOF SEALING SIDES EACH OF WHICH IS PRESSED AGAINST THE OTHER MEMBER, AND IN WHICH THE ENDS OF THE GAPS BETWEEN FIRST STRIP MEANS IN SAID SEALING SLIDES AND THE RESPECTIVE ADJACENT PORTIONS OF SAID OTHER MEMBER IS COVERED BY COVER STRIPS ARRANGED IN GROOVES PROVIDED IN SAID POCKET CONTAINING MEMBER AND EXTENDING IN THE DIRECTION OF DISPLACEMENT OF SAID SEALING SLIDES, MEANS BEING PROVIDED FOR SEALINGLY PRESSING SAID COVER STRIPS   AGAINST SIDE WALL PORTIONS OF SAID OTHER MEMBER AND AGAINST ADDITIONAL STRIPS RESPECTIVELY LOCATED IN LATERNAL GROOVES OF SAID SEALINGLY SLIDES.

Jan. 5, 1971 SCHRbDI-IR ETAL 3,552,894

SEALING STRIP Filed Aug. 27, 1968 4 Sheets-Sheet 1 [*H FIG] Prior A r! In v en lors /l eraer 75401: 146/7223; o e r Z/aaf 71 p- Jan. 5, 1971 W.J.H.SCHRODER ETAL 3,552,894

SEALING STRIP Filed Aug. 2.7, 1968 4 SheetS-Sheet 2 FIGS In venlors fl prker Z1000 A e/m 00h rov I Jan. 5, i971 w.J.. H. SCHRDDER ErAL 3,552,894

SEALING STRIP Filed Aug. 27, 1968 4 Sheets-Sheet 3 I FIGS 20 1971 w. J. H. SCHRODER ET L SEALING STRIP Filed Aug. 27, 1968 4 Sheet-Sheet 4t In veniors:

United States Patent 3,552,894 SEALING STRIP Werner Johann Hermann Schriider, Rudolf Prescher, and Peter Klaus .lurgen Miiller, Essen, Germany, assiguors to Fried. Krupp Gesellschaft mit beschrankter Haftung, Essen, Germany Filed Aug. 27, 1968, Ser. No. 755,644 Claims priority, application Germany, Sept. 2, 1967, 1,576,896 Int. Cl. F01c 19/00 US. Cl. 418-139 1 Claim ABSTRACT OF THE DISCLOSURE A rotary piston machine in which one of two members rotatable relative to each other has guided in pockets thereof sealing slides each of which is pressed against the other member, and in which the ends of the gaps between first strip means in said sealing slides and the respective adjacent portions of said other member is covered by cover strips arranged in grooves provided in said pocket containing member and extending in the direction of displacement of said sealing slides, means being provided for sealingly pressing said cover strips against side wall portions of said other member and against additional strips respectively located in lateral grooves of said sealing slides.

Rotary piston machines operating as displacer pumps or as displacer motors have pressure chambers which are separated from each other by sealing strips. These sealing strips are displaceably guided in pockets in radial or axial direction and by springs or liquid pressure are pressed against the rotary piston. Such pockets are preferably located in the housing of the rotary piston machine. Since the rotary piston is eccentrically mounted or is of a non-round design, it will when rotating bring about a back and forth movement of the sealing strip or slide in said pockets while alternately liquid is pressed out of one pressure chamber or a group of pressure chambers and simultaneously liquid enters the other pressure chamber or pressure chambers. Consequently, a different liquid pressure prevails in two pressure chambers at opposite sides of a sealing slide. It is necessary that the sealing slides effect a proper seal with regard to this difference in pressure.

It is an object of the present invention to provide a sealing strip construction which will meet all requirements concerning a seal between pressure chambers of rotary piston machines, even if due to certain conditions of operation deformations of structural elements should occur which move relative to each other.

This object and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawings, in which:

FIG. 1 diagrammatically represents a crosssection through a heretofore known rotary piston machine.

FIG. 2 is a section taken along the line IIII of FIG. 1.

FIGS. 3, 4 and 5 respectively illustrate three axial sections of portions of a hydrostatic drive with a sealing slide according to the invention, said slide being displaceable in radial direction and being of different design in FIGS. 3, 4 and 5 respectively.

FIG. 6 is a section taken along the line VIVI of FIG. 5.

FIG. 7 represents an axial section through a portion of a hydrostatic drive with axially displaceable sealing slides according to still another embodiment of the invention.

FIG. 8 shows the development of the cylinder of FIG.

3,552,894 Patented Jan. 5, 1971 "ice 7 taken along the line VIIIVIII of FIG. 7 and placed into the drawing plane.

Referring first to the prior art rotary piston machine shown in FIGS. 1 and 2, this rotary piston machine comprises a housing 1 which has a cylindrical opening housing an output shaft 3. A rotary piston 4 is rotatable about the axis 2 of the output shaft 3 while being eccentrically mounted on the latter. The rotary piston 4 is in the shape of a cylinder. The annular gap resulting from the eccentric mounting of the rotary piston and located between the housing 1 and the rotary piston 4 is by means of four sealing slides 5 uniformly subdivided into four pressure chambers 6, 7, 8 and 9. The sealing slides 5 are radially displaceable in pockets 10 of the housing .1. By means of non-illustrated springs or by liquid pressure, the said sealing slides 5 are pressed against the circumferential surface of the rotary piston 4.

When the rotary piston 4 rotates, the volumes of the pressure chambers 6, 7, 8, 9 change together with a cyclic pressure change inherent thereto. Therefore, in two adjacent pressure chambers different liquid pressures prevail. In order to assure that in spite of this pressure differenct no material quantities of liquid will pass from one pressure chamber to the other, it is necessary to provide an effective seal between the pressure chambers. The heavy lines 11, 12, 13 indicate the critical gaps in FIG. 2 which in case of an insufficient seal would permit the passage of unduly large quantities of liquid from one pressure chamber to the other pressure chamber. The gap involved is marked by the line and is located between the face edge of the sealing slide 5 and the circumferential surface of the rotary piston 4. Also the gaps marked by the lines 12 between the lateral surfaces of the rotary piston 4 and the inner side surfaces of the opening in the housing 1 and the gap marked by the line 13 between the lateral surfaces of the slide 5 and the inner side surfaces of the housing opening are involved in this connection.

Attempts have been made to realize the required seal in the critical gaps by close fits between the parts 1, 4, 5 which are to be sealed relative to each other. This, however, required correspondingly close finishing tolerances and resulted in high manufacturing costs which in many instances cannot be tolerated. This applies above all to rotary piston machines of large dimensions in which the finishing tolerances cannot be held so low that a suflicient gap seal can be obtained. Moreover, especially with high output rotary piston machines working with liquid pressures, the fit cannot be made as narrow as desired because provision has to be made that the structural elements which move one upon the other will deform due to alternating pressure loads and alternating temperatures.

In order to be able to provide a satisfactory seal at least at the critical gap marked by the line 11, the sealing slides are provided with sealing strips as indicated in the lower portion of FIGS. 1 and 2. Such sealing strip 14 is guided in radial direction in a slot of slide 5 which slot is open toward the rotary piston 4. The sealing strip 14 is, for instance, by means of springs 15 pressed against the circumferential surface of the rotary piston 4. The sealing strip 14 extends over the width of the rotary piston 4. This, however, does not yield a satisfactory seal in the critical gaps marked by lines 12 and 13.

In an effort to overcome the above mentioned drawbacks, the present invention is based on a sealing strip construction on a sealing slide which is displaceably guided in a pocket of one of two structural members of a rotary piston machine, for instance the housing or the rotary piston, which are rotatable relative to each other. The said sealing slide has in a slot an end face strip which extends over the elfective width of the rotary piston and which by means of a spring element or the like is pressed against the other structural member. The invention consists primarily in that the gap between said end face strip and the other structural member is on both ends covered by two cover strips which are arranged approximately parallel to the direction of displacement of the sealing slide in grooves of the structural member containing the pocket. The said cover strips are by means of a spring element or the like pressed against the lateral surfaces of the other structural element, against the end surfaces of the face strip and against two leg strips which are located on both sides of the sealing slide in grooves substantially parallel to the direction of displacement of the sealing slide.

The invention may be used for instance in connection with hydrostatic drives as disclosed for instance in US. Patent 3,066,476 and, more specifically, with radial as well as with axial guiding of the sealing slide. If desired, the sealing slide may also be guided in pockets of the rotary structural member instead of in pockets of the housing.

Referring now to FIGS. 3, 4 and 5 showing three embodiments according to the present invention, the hydrostatic drive shown in these figures has a housing 20 with a rotary piston 21 therein, said rotary piston having an oval profile. The lateral surfaces 22 of the hydrostatic drive form together with the lateral surfaces 23 of the housing opening very narrow gaps. The housing 20 has pockets 24 uniformly distributed over the circumference of its opening, only one pocket 24 being shown. Each pocket 24 has radially displaceably guided therein a sealing slide 25. The small lateral surfaces 26 of said sealing slide 25 form together with the narrow inner surfaces 27 of pocket 24 very narrow gaps of for instance a few hundredth of a millimeter. In a similar manner, narrow gaps are formed between the wide lateral surfaces of the sealing slide 25 and the wide inner surfaces of the pockets 24. By means of non-illustrated springs or by means of liquid pressure which in the pocket 24 acts upon that side of the sealing slide 25 which faces away from the rotary piston 21, the slide 25 is pressed in this direction toward the rotary piston 21.

According to the embodiment of FIG. 3, the slide 25 is provided with a strip 28 which corresponds to the strip 14 in FIGS. 1 and 2. This strip 28 is guided in a slot 29 of slide 25 which slot is open toward the rotary piston 21. By means of springs 30 the strip 28 is pressed against the circumferential surface of the rotary piston 21. The length of the strip 28 substantially equals the width of the rotary piston 21. Consequently, the end faces 31 of strip 28 are located in the same planes as the lateral surfaces 22 of the rotary piston.

On both sides of the rotary piston 21 in housing 20 there are provided grooves 32 which extend parallel to the direction of displacement of the sealing slide 25 and which toward the housing opening and in part toward the pocket 24 are open.

Cover strips 33 are provided in grooves 32 and by means of springs 34 are pressed against the lateral surfaces 22 of the rotary piston 21 and against the end faces 31 of the strip 28. Furthermore, the cover strips 33 have those portions thereof which extend into pockets 24 in engagement with two leg strips 35 which are arranged in grooves 36 of the sealing slide 25 in parallel arrangement to the direction of displacement of slide 25 while being pressed by springs 37 against the cover strips 33.

Thus, the cover strips 33 cover the gap between the strip 28 and the rotary piston 21. As a result thereof, a sutficient seal is obtained not only by the strip 28 within the area of the circumferential surface of the rotary piston 21 but also at both sides of said piston 21. Consequently, no material quantity of liquid can pass from one of the pressure chambers on either side of the slide 25 to the other pressure chambers along the surfaces 31 of the strip 28. Since, according to this embodiment, each of the sealing strips 28, 33, 35 is individually displaceable transverse to its engaging surface, the sealing strips will accomplish their purpose also when the engaging surfaces have worn.

Preferably, all sealing strips 28, 33, 35 have engaging surfaces of the same width.

FIG. 3 shows the sealing slide 25 in a posittion in which it is moved out farthest of the pocket 24 while the length a of the engaging surfaces between the rotary piston 21 and the cover strip 33 is shortest during a revolution of the rotary piston. Depending on the selected dimensions of the cover strips 33 it may sometimes happen that the distance a is so short with regard to the total length of the cover strips 33 that the ends of the cover strips which protrude beyond the rotary piston 21 and the strip 28 will tilt in the direction toward the slide 25 in which instance the springs 37 will not offer sufiicient resistance to the pressure pressing the strip 35 into the groove 36. With such tilting movement of the strips 33, the latter would no longer properly engage the lateral surfaces 22 of the rotary piston and the end surfaces 31 of the strip 28 with the result that a sufiicient seal would no longer be realized.

These disturbances which might occur are prevented for instance by an arrangement according to FIG. 4 according to which the strips 34 form a rigid unit with the strip 28 so that a U-shaped sealing strip is formed the legs of which are non-yieldable against lateral pressure. The cover strips 33 are in this instance by means of springs 34 pressed simultaneously against the lateral surfaces 22 of the rotary piston 21 and against the lateral surfaces of the U-shaped sealing strip.

Another possibility of preventing the above mentioned tilting of the cover strips is illustrated in FIGS. 5 and 6. According to the arrangement shown in these figures, the leg strips 35 are again separated from the strips 28 and are arranged in grooves 36 on both sides of the slide 25. However, in this instance the leg strips 38 are of a design which differs from that of the leg strips 35 of FIG. 3. More specifically, the strips 38 have a groove 39 which is open toward the lateral surfaces 27 of the pocket 24. The pocket 24 is at its longitudinal sides and at the transverse side which faces away from the rotary piston 21 surrounded by engaging surfaces by means of which the strip 38 engages the respective side surface 27 and, when the sealing slide has moved out, partly engages the respective side surface 23 of the housing opening. This is brought about by the effect of a liquid pressure prevailing in groove 36 and acting upon the inner side of the strip 38 because the said groove 36 communicates with the slot 29 receiving the strip 28 and through a bore 40 of slide 25 communicates with that portion of the pocket 24 which is located opposite to the rotary piston 21.

As shown in FIG. 6, the leg strips 38 have a greater width than the cover strips 33 which latter have the same width as the strips 28. The cover strips 33 extend by means of their portions protruding beyond the piston 21 and strip 28 into the grooves 39 of the strips 38, but only to such an extent that they do not prevent the engagement of the surfaces 27 and 23 by the strips 38. The groove 39 of each leg strip 38 is through bore 41 in communication with that portion of groove 36 which is located on the inner side of the leg strip 38. Therefore, in groove 39 there prevails the same liquid pressure as in groove 36. Furthermore, this liquid pressure is maintained also in the groove 32 receiving the cover strip 33, because this last mentioned groove portion communicates with the groove 39 of strip 38 through a gap 42 which is widened by a slanted portion 43.

In view of the liquid pressure prevailing in groove 32 of each cover strip 33, the cover strip 33 is pressed against the respective lateral surface 22 of the rotary piston and the end surface 31 of the strips 28 so that no springs are required for this purpose. That portion of each cover strip 33 which protrudes beyond the rotary piston 21 and the end strip 28 is in view of the above mentioned connection between groove 39 and groove 32 at its sides which are located opposite to each other acted upon the same liquid pressure. Consequently, that portion of each cover strip 33 which protrudes beyond the rotary piston 21 and the end strip 28 is not acted upon by a force transverse to said cover strip 33. Consequently, the cover strips 33 are not subjected to any tilting moments so that a proper engagement of the lateral surfaces 22 of the rotary piston and the end faces 31 of the strip 28 by the cover strips 33 will be assured.

Groove 39 of each leg strip 38 ends in the direction toward the rotary piston 21 in a slot by means of which the leg strip 38 extends over the strip 28.

According to the embodiment of FIGS. 7 and 8, the rotary piston is formed by two discs 51 mounted on a shaft 50 and by annular bodies 52 arranged on said discs 51. These annular bodies 52 move tightly in annular recesses of the housing 54 while a web 55 of the housing is located between said annular recesses. The annular bodies 52 have two equidistant wave-like surfaces 56 engaged by sealing strips 57 which are axially displaceably guided in continuous recesses in web 55 and form pressure chambers 58.

Each sealing slide 57 is sealed with regard to each of the two wave-shaped surfaces 56 and on both sides with'regard to the housing by means of a strip 28 and two leg strips 35. The leg strips 35 are united for instance according to the embodiment of FIG. 4 so as to form a U-shaped sealing strip. The leg strips 35 are similar to the embodiment of FIG. 4 in engagement with cover strips 33 which are arranged in grooves 56 of the housing 54 in parallel relationship to the direction of displacement of the sealing slide and are by springs or liquid pressure pressed against the lateral surfaces of the rotating annular bodies 52. In this way, similar to the other embodiments referred to above, the required seal of all critical gaps will be assured.

It is, of course, to be understood that the present invention is, by no means, limited to the particular embodiments shown in the drawings but also other modifications are possible, the invention being defined by the scope of the disclosure.

What we claim is:

1. A rotary piston machine which includes: a first member forming a housing, a second member at least partially arranged within said first member and forming a piston, said first and second members being rotatable relative to each other while defining with each other a gap varying in the course of a relative rotation of said members with regard to each other, one of said members being provided with a plurality of first recess means, a plurality of sealing slide means respectively extending into said gap and reciprocable in said first recess means in response to a relative rotary movement of said first and second members with regard to each other, each of said sealing slide means including a first sealing strip in sealing engagement with the surface faced thereby and pertaining to the other member to sealingly subdivide said gap into a plurality of chambers, each of said sealing slide means having its lateral end faces provided with second recess means extending in the direction of the respective sealing slide means containing said second recess means, second sealing strips respectively arranged in said second recess means, that one of said members which is provided with said first recess means also being provided with confining walls respectively arranged on and adjacent to the side surfaces of the other member, said confining walls respectively being provided with groove means extending in the direction of displacement of said sealing slide means and in the area of the respective adjacent first and second sealing strips and the adjacent side wall of said other member, and third sealing strips respectively arranged in said groove means and in sealing engagement with the respective adjacent side wall of that other member and with the adjacent surfaces of the adjacent first sealing strip, each said second sealing strip being positioned against the adjacent side wall of said first recess means and having a groove open to this side -'wall but closed to a gap between said sealing slide means and this wall, said groove receives that portion of the third sealing strip protruding over said first sealing strip and is connected by passage means to the groove means in which said third sealing strip is arranged, further passage means connecting said groove means receiving said third sealing strip to said first recess means so that the fluid pressure prevailing in this recess means and in said groove and groove means prevents said third sealing strip from tilting, and said further passage means also permitting fluid pressure to act on said second sealing strip to press it against the wall of said first recess means.

I References Cited UNITED STATES PATENTS 280,194 6/1883 Lipsey 91-73 379,112 3/1888 Hemsath 9l-73 695,006 3/1902 Stowell 123--8SS 753,388 3/1904 Groves, Sr. 1238SS 819,276 5/1906 Heunsch 1238SS 1,350,231 8/1920 McFarland 123-8SS 3,151,784 10/1964 Tailor 1238SS 3,437,079 4/1969 Odawara 103--l21X FOREIGN PATENTS 58,490 9/1911 Switzerland 103123 MARTIN P. SCHWADRON, Primary Examiner I. C. COHEN, Assistant Examiner U.S. Cl. X.R. 418243 

